This invention relates in general to certain new and useful improvements in frequency equalizers and, more particularly, to frequency equalizers which employ a unique resonant circuit and which serve as tunedfilters to create a symmetrical feedback around the main operational amplifier of the frequency equalizer.
It has recently been recognized that frequency equalizers can find effective employment both in professional and non-professional audio fidelity systems. Frequency equalization for the various octave bands in a sound reproduction system has been used for some time in professional audio fidelity equipment, as for example in recording studios and the like. More recently, there have been some frequency equalizers which have been offered commercially for the non-professional market, that is for the home use market. These frequency equalizers are designed to provide discrete octave equalization control of a plurality of octaves in each sound reproduction channel.
These frequency equalizer systems are designed in order to accommodate for room changes and for equalization of various forms of recording mediums, as for example, various types of records. In addition, compensation for radio stations can be obtained by these equalizing systems where some of the stations are noted for excesses in either high or low frequencies. In addition, these frequency equalizer systems are designed for use in equalizing tapes such that the home user can perfectly equalize tape recordings.
Nevertheless, in order to obtain a reasonable market for these frequency equalizers, the producers thereof have attempted to economize in the design and manufacture of these systems which thereby limits the overall versatility and, more particularly, the effectiveness of these frequency equalizer systems. While the professional market does, nevertheless, create a sufficient demand for a more versatile and high-performance frequency equalizer, the non-professional market is only available to frequency equalizers which are capable of being marketed at a relatively low unit cost. Consequently, the producers of the presently available frequency equalizer systems have compromised by merely utilizing the design of the professional equipment and attempting to reduce the same to a consumer compatible market.
Notwithstanding, the deficiencies in the designs of these equalizer systems have seriously hampered the overall effectiveness of the commerically available frequency equalizers. Each of these frequency equalizers utilize some form of tuning circuit for each of the major octave bands for each of the recording and reproducing channels. Nevertheless, the present attempts to produce a home market frequency equalizer system which relies upon the professional design have compromised the effective versatility and efficiency of these equalizer systems since there has been no attempt to redesign the equalizer system and particularly the resonant circuit therefor.
It is therefore the primary object of the present invention to provide an audio fidelity frequency equalizer system which is capable of efficiently controlling the frequency response of each of the octave bands in each of the channels of a sound reproduction or recording.
It is another object of the present invention to provide an audio fidelity frequency equalizer system of the type stated which is constructed with a high degree of quality and is capable of rendering the desired frequency outputs on a relatively low distortion free level.
It is a further object of the present invention to provide an audio fidelity frequency equalizer system of the type stated which is highly reliable in its construction and which can be constructed at a relatively low unit cost.
It is an additional object of the present invention to provide an audio fidelity frequency equalizer system of the type stated which is capable of recducing the effects of hum and other electrical noise resulting from low level switching in the input circuits to the frequency equalizer system.
It is also an object of the present invention to provide an audio fidelity frequency equalizer system of the type stated which is capable of handling inputs of a wide dynamic range and stabilizing the frequency outputs thereof with a very low distortion factor which are relatively noise-free.
With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement and combination of parts presently described and pointed out in the claims.